As bicycle theft accidents increase, a variety of locking devices has been proposed. However, thefts are not still reduced because of thieves aiming for structural weak points. As illustrated in FIG. 1, a conventional locking device configured to constrain wheels is problematic in that it is difficult to prevent the commission of thefts for wheels other than the constrained wheel, and a weak spoke may be damaged, namely, bent or broken by impact applied while the bicycle is stored.
Meanwhile, the locking device illustrated in FIG. 2 adopts a method of fixing a bicycle by holding a frame corresponding to a body of the bicycle, thus ensuring more secure locking and achieving higher security effects. However, since all bicycles should have mounts at uniform heights and positions to facilitate a coupling operation, this locking device may be applied to public bicycles having uniform sizes and shapes, but may not used for private bicycles having various sizes and shapes.